Soulmates found one story at a time.

Gustav is a hulking minion with shaggy white hair, white-eyes, and three scars across his throat,  who works for the Wolf Mage

He was involved with the gang who kidnapped Ember, Musette, and Poppy

After Ember and Musette escape, by knocking Gustav out and taking his Mage-Maker blade, he tracks them in his wolf form.